Răspuns:
216 RON
Explicație pas cu pas:
a = suma de bani a Dariei
In prima zi a cheltuit a/2 RON
In a doua zi a cheltuit 1/3 ·(a-a/2) = 1/3(a/2) = a/6 RON
In a treia zi = 1/2 ·(⁶⁾a - ³⁾a/2 - a/6) = 1/2·(2a/6) = a/6 RON
In a patra zi = 1/3·(⁶⁾a-³⁾a/2-a/6-a/6) = 1/3·a/6 = a/18 RON
Rest = 24 RON
¹⁸⁾a = ⁹⁾a/2 + ³⁾a/6 + ³⁾a/6 + a/18 + ¹⁸⁾24 =>
18a = 9a+3a+3a+a+432 =>
18a - 16a = 432
2a = 432
a = 432:2
a = 216 RON
